1. Field of the Invention
This invention relates generally to semiconductor processing, and more particularly to circuit boards with solder interconnect pads and to methods of making the same.
2. Description of the Related Art
Various conventional organic semiconductor chip package substrates interface electrically with a flip-chip mounted semiconductor chip by way of multiple solder bumps. In some conventional designs, the solder bumps or portions thereof are positioned in holes formed in a solder mask that is the outermost layer of the circuit board. The holes are intended to be vertically registered with underlying bump pads. In conventional designs, the bump pads are fabricated with a lateral dimension that is larger than the solder mask hole. This creates an interface between the solder mask and the upper surface of the bump pad.
The conventional solder interconnect pads are typically formed on underlying vias. At these locations, the solder mask can be subjected to bending moments. These bending moments can cause delamination of the solder mask at the bump pad upper surface. Delamination can produce pathways for solder from an overlying bump to migrate laterally and potentially short to adjacent conductor structures, such as traces or other bump pads.
There is an on-going trend to squeeze more routing into circuit boards, particularly semiconductor chip package substrates. The need for greater routing complexity is caused by, among other things, increases in the number of input/outputs of ever more complex semiconductor die designs. It is not a trivial matter to insert more traces and vias into a circuit board layout. Indeed, the goal of increased routing must compete with design rules, which are put in place to ensure that manufacturing processes used to form the circuit board can do so reliably.
However, conventional techniques to address potential solder mask delamination often resort to enlarged bump pads or design rules that require greater conductor spacing, both of which weigh against greater packing density.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.